Me thinks that you worry to much. The power in your system is ~220v 60
cycle. The speed of the motor, or converter is determined by the
construction of the motor, i.e. the number of poles in the motor. You need
to worry about the power, not the speed. As long as the motor is turning at
~rated speed it will generate 60 cycles regardless. I also run a two speed
motor on my mill with no problems from the converter.
lg
no neat sig line.

"Artemia Salina" wrote in message
news
Here's the situation. I have a lathe which currently
uses a single phase motor with a 145T frame. I want
to replace it with a 3 phase unit with the same frame
type, but the only motors I can find with that frame
and in the less-than-2-horse-power range run at
1140 RPM. I have a (1725 RPM) rotary phase converter
which powers another 3 phase motor in my miller. The
miller's motor is a dual speed motor (I don't know
the RPM of the two speeds, but "fast" is double the
speed of "slow". This is the stock motor in a Hardinge
TM/UM miller).

I know that adding idling motors into the circuit of a
rotary phase converter will effectively increase the
capacity of the converter, so the various motors do have
an effect on the 3 phase generation system. My question is,
will all of these different RPM motors adversely effect the
operation of the rotary converter or the quality of the
3 phase power it generates? I doubt I'll ever have both
machines running at the same time, but who knows.